Incontestably
The Century Dictionary and Cyclopedia
So as not to be contested or disputed; in a manner to preclude debate; indisputably; incontrovertibly; indubitably.
Wiktionary, Creative Commons Attribution/Share-Alike License
adverb.
In an
incontestable
manner.
Word Usage
"Radium's discovery marked "incontestably" as Curie claimed, a new epoch for chemists and a kind of chemistry that we might well call "the chemistry of the imponderable.""